Accessory Dwelling Units

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An ADU (accessory dwelling unit) is an additional, self-contained dwelling on a single-family lot. It can be attached, such as in the lower level of the main dwelling, or detached at the rear of the property, such as above the garage. An ADU is smaller in size than the main dwelling, but is maintained under the same ownership of the property and cannot be a fee simple condo. 

These smaller units represent the “missing middle,” filling the gap between single-family homes and multi-unit dwellings downtown. While ADUs are not the sole answer to Decatur’s missing middle, they represent a big step in the right direction. Residents of ADUs contribute to the vitality of the community, and the additional income from ADUs makes it possible for more families to own and maintain a home in the city. 

ADUs as a housing type became effective in 2015 under the new Decatur Unified Development Ordinance. They are allowed in most single-family and multi-family residential zoning districts – R-85, R-60, R-50, RM-18, RM-22, and RM-43. One ADU per primary dwelling unit is possible if the lot conforms to the minimum size requirements of its zoning district. Other considerations: 

  • An ADU may be developed in or to the rear of an existing or new main dwelling. 
  • To keep true to its accessory size, an ADU may have a floor area between 300 and 800 square feet, and should not exceed 40 percent of the floor area of the main dwelling. 
  • An ADU may have up to two bedrooms and no more than two occupants. 
  • The owner of the property is required to reside in either the main dwelling or the ADU for at least eight months of the year. 
  • If detached from the main dwelling, an ADU must be located in the rear yard and have a footprint no greater than 30 percent of the rear yard. If the ADU is combined with the garage, the total floor area may be up to 1,000 square feet. 
  • In combination with the main dwelling, the total floor area should not exceed 40 percent of the lot area. 
  • Similarly, the total lot coverage of all impervious surfaces should not exceed 40 percent of the lot area. 

As a housing option, ADUs demonstrate the values of inclusivity, diversity, and affordability promoted by the City of Decatur. They serve to fill a gap in Decatur’s housing market by providing a new, neighborhood scale rental housing option for those looking for affordable living arrangements in a more traditional single-family-home setting.